Leaks in pipelines carrying hazardous liquids are a growing problem. An expansion of leak events, combined with an increasing amount of pipeline infrastructure near urban centers and environmentally sensitive areas, has renewed the focus on the detection of leaks in hazardous liquid pipelines
Most of today's pipeline leak detection systems are unable to detect small leaks, for example, leaks less than 1% of the pipeline throughput. Furthermore, detection systems aimed at detecting small leaks have high rates of false alarms. High false alarm rates result in leak detection systems that are ultimately ineffective because the alarms are ignored.
Hazardous liquid leak detection systems for continuous monitoring can be categorized into internal leak detection systems and external leak detection systems.
Internal leak detection systems use measurement sensors providing flow or pressure readings, and perform calculations to estimate the state of the fluids within the pipe. Examples of internal leak detection systems are volume balance, rate of pressure/flow change, pressure point analysis, negative pressure waves, mass balance, real-time transient modeling.
External leak detection systems use dedicated instrumentation equipment, located externally to the pipe, to detect escaped fluids. Examples of common external leak detection systems are those using acoustic sensors, fiber optic cables, temperature sensing cables, liquid or vapor sensing cables, and imaging systems.
A conventional approach to using an imaging system for leak detection is to use infrared or thermal imaging. Certain hydrocarbons absorb infrared radiation, which makes it possible to detect leaks with infrared cameras. The thermal conductivity in wet (leak-saturated) ground is different than in dry ground, which also allows thermal imaging to detect leaks.